The present invention relates to brushless D.C. motors in general, and particularly to a disk storage drive equipped with a brushless D.C. motor.
In disk storage devices bits representing data are stored in circular tracks on rigid or flexible disks which are rotated at relatively high speeds. Bits are inscribed or read by a read/write head which must be accurately positioned relative to the particular track which is being inscribed or read. This means that the disks must rotate absolutely true, or as close to it as possible.
To impart rotation to such disks it is known to arrange the electric drive motor axially below the disk and to connect the disk via suitable connecting elements to the motor shaft for rotation therewith. This, however, is disadvantageous because the upper of the two motor-shaft bearings is subjected--not the least because of the high-speed rotation--to greater stresses than the lower one. As a result, the disk will soon no longer rotate true and reading and writing errors will develop.
According to another proposal the motor is located somewhat higher, so that the disk is positioned in a plane which is axially adjacent (i.e., as considered with reference to the axis of rotation) to the upper bearing of the motor. The connecting elements are shaped differently than in the first-mentioned construction, but they still connect the disk with the motor axis. This means that although the disadvantages of the first-mentioned construction are somewhat alleviated in this second proposal, they still do exist.
Still another proposal, contained in U.S. Pat. No. 4,101,945, provides for the connection of the disk to the motor shaft above the motor, but arranges the bearing system intermediate the disk and the motor.
Common to all this prior art is the connection of the disk to the motor shaft, which requires relatively complicated connecting structure without, however, being able to assure optimum uniformity of load distribution to all bearings of the motor-shaft bearing system.